This application is a divisional application of U.S. patent application Ser. No. 11/284,649, filed Nov. 22, 2005, which is a Continuation-In-Part of U.S. patent application Ser. No. 10/757,294, which issued as U.S. Pat. No. 7,008,997, which is a Continuation-In-Part of U.S. patent application Ser. No. 10/223,991, each of which is incorporated herein by reference in its entirety.
The present invention relates generally to a system and method of inhibiting the growth of onychomycosis (toe fungus) and skin conditions such as urushiol-induced allergic contact dermatitis (poison ivy, oak and sumac reactions), and in particular to a polymer chemistry device that provides a hydrophobic, elastomeric topical agent for inhibiting the growth of these conditions and for mitigating of the deleterious effects thereof.
Onychomycosis is a fungal infection of the nails commonly known as toe fungus, although it also attacks fingernails. Onychomycosis is caused primarily by dermatophytes, a type of fungi, such as Trichophyton rubrum and Trichophyton mentagrophytes. Yeasts such as Candida albicans cause a small number of cases, usually fingernail infections, and molds such as Scopulariopsis, Scytalidium, Acremonium, and Fusarium cause additional cases. Dermatophytes grow in the nail bed beneath the nail, and live off keratin, the protein in the nail. The condition usually begins towards the far end of the nail and may start with patches of white or yellow discoloration.
If the condition is left untreated, it will proceed to the base of the nail. It will attack the nail root (matrix) and cause the nail to grow very thick and deformed. The big toe is usually the first nail to be affected with the condition spreading to adjacent nails. In rare cases this condition can also affect the skin surrounding the nails. Debris may collect under the nail, causing a foul smell. The nail may thicken and become flaky. Thick toenails, in particular, may cause discomfort in shoes and may even make standing and walking painful for the affected individual. Onychomycosis of the fingernails may restrict typing, writing, and computer work; dressing; manual dexterity, fine touch, and sensitivity; and social interaction.
There are four types of onychomycosis. Distal and/or lateral subungual onychomycosis affects the nail bed and nail plate. Proximal subungual onychomycosis affects the proximal nail fold, with infection extending distally under the nail plate. Superficial white onychomycosis affects the top of the nail plate. Candidal onychomycosis affects the nail, skin, and mucous membranes.
Onychomycosis is often treated with terbinafine, an oral or topical antifungal agent (brand name: Lamisil®). Terbinafine is attracted to keratin, the food source of dermatophytes. Terbinafine acts by interfering with the ability of fungi to make sterols, which are an important part of the membrane that surrounds fungal cells and holds them together. Depriving the fungi of sterols weakens the cell membrane. Terbinafine is prescription medication. Topical terbinafine was approved by the FDA in 1993, and terbinafine oral tablets were approved in 1996. Other antifungal agents used the treatment of onychomycosis are griseofulvin (Fulvicine®; Gris-Peg®) and itraconazole (Sporanox®).
While medications for treating onychomycosis are readily available, they are prescription drugs that must be dispensed by a licensed medical professional. This usually requires that an individual suffering from onychomycosis be examined by a doctor, an expense many people cannot afford. Additionally, the prescription drugs themselves are expensive, and must be taken according to a dosing regimen, often for several months.
Poison ivy, oak, and sumac belong to a family of plants that produce urushiol, an oil that causes one of the most common allergic reactions in the United States. Experts estimate that up to 70% of the U.S. population is allergic to urushiol. The American Academy of Dermatology estimates that there are up to 50 million cases of urushiol-induced dermatitis annually in the United States alone. It accounts for 10% of all lost-time injuries in the United States Forest Service.
The allergen urushiol attaches to the skin within five minutes to two hours after exposure, most commonly by physical contact with the leaves or sap of plants such as poison ivy (Toxicodendron radicans or Rhus toxicodendron), poison oak (Toxicodendron diversilobum or Rhus diversiloba), or poison sumac (Toxicodendron vernix or Rhus vernix). Chemically, urushiol is harmless to humans. However, it binds to skin cell membranes and initiates a T-cell mediated immune response. That is, urushiol changes the configuration of skin cell membranes, so that the body's immune system no longer recognizes these cells as belonging to the body and attacks them as foreign. The result is an allergic eczematous contact dermatitis characterized by redness, swelling, papules, vesicles, bullac, and streaking. The dermatitis causes itching, and excessive scratching may lead to infection.
Zanfel® and Tecnu® are commercial preparations that remove urushiol from the skin, if applied immediately following exposure. However, they are less effective once an outbreak has occurred. Calamine lotion, antihistamines, and hydrocortisone ointment are over-the-counter treatments commonly used to abate the symptoms of urushiol-induced allergic contact dermatitis once an outbreak develops. A dermatologist may prescribe a course of corticosteroids to neutralize the itch. Commonly prescribed drugs are prednisone and betamethasone dipropionate (Diprolene®). These drugs require the inconvenience and expense of an examination and prescription by a dermatologist. A variety of home remedies are known (or alleged); most are ineffective.
A need exists in the art for an inexpensive, non-prescription, safe, easily applied device that inhibits the growth of onychomycosis and urushiol-induced allergic contact dermatitis, and that alleviates or at least mitigates the deleterious effects of these conditions.